KVM: arm64: selftests: get-reg-list: Remove get-reg-list-sve

Now that we can easily run the test for multiple vcpu configs, let's
merge get-reg-list and get-reg-list-sve into just get-reg-list. We
also add a final change to make it more possible to run multiple
tests, which is to fork the test, rather than directly run it. That
allows a test to fail, but subsequent tests can still run.

Signed-off-by: Andrew Jones <drjones@redhat.com>
Reviewed-by: Ricardo Koller <ricarkol@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20210531103344.29325-5-drjones@redhat.com